Every day, in response to user queries, millions of data operations are carried out. In particular, data operations such as update, add or remove operations, also result in changes of entities stored in a database. In a large-scale database system, where databases and their replicas are often distributed across multiple database servers, in many situations not all write operations are immediately applied across the multiple database servers. In other cases, data operations are applied in one database but not all replicas of the database. Notwithstanding delays in applying data operations to entities stored in a database or its replicas, users expect some entity changes to become immediately observable, such as entity changes that result from their own recent activity.